Dynamic behaviours of piston rings and their practical impact. Part 2: Oil transport, friction and wear of ring/liner interface and the effects of piston and ring dynamics

Abstract

The paper discusses several important processes that have great impact on the lubrication between the top two rings and the liner. The analysis is conducted on the basis of the calculation results on a heavy-duty (HD) diesel engine using theoretical models. Oil supply mechanisms to different liner regions are analysed, and emphasis is given to the oil transport to the top liner region that is found critical to friction, wear and oil consumption in HD diesel engines. Additionally, the paper discusses the oil supply to the second ring, its uncertainties and the effect on the prediction of the performance of the top two rings. Furthermore, the effects of dynamics of the piston and rings on friction, wear and oil transport are illustrated and the effects of bore distortion on oil transport are discussed. For practical purposes, a formula to describe the second ring running surface profile is given based on simple geometrical constraint. A new truncation method is rendered for plateau surface roughness in order to effectively use the existing mixed lubrication models.